With the use of certain engines, particularly reversible marine engines, which are capable of running either in a forward or a reverse direction for propelling the vessel accordingly, it is necessary to use extreme care in assuring that the engine has stopped running in one direction or at least slowed down to a safe rate of rotation before an attempt is made to reverse and restart the engine for propelling the vessel in an opposite direction. Since operation of a marine vessel and its engine is normally controlled by a controller usually located on the boat at a point remote from the engine house, the operator must rely on experience or perhaps indicating means, such as visual instruments, for apprising him when to make each move of the controller handle when desiring to reverse direction of rotation of the engine. Such movements may require the operator to first place the handle in an engine stop position, then, after checking the instruments to assure himself that the engine has stopped, move the handle to the start position for initiating the opposite direction of rotation, and finally into the desired speed position. With such a control apparatus, where so much attentiveness, reliance on instruments, and manipulation of the controller handle is required of the operator, the possibilities of resultant damages from movement of the controller handle into one of the required positions, perhaps in reliance on information indicated on a faulty instrument, before the rotating condition of the engine is compatible with the operation called for by the handle position, are greatly increased.